Bamboo pulp fiber (BPF) was treated by nano CaCO3 impregnation modification(IM), and IMBPF/epoxy resin composites was prepared by means of vacumm assisted resin infusion(VARI)technology. Thermal degradation behavior of raw materials and composites was studied by thermo gravimetric method(TGA) under nitrogen atmosphere. Also, the apparent activation energy of the composite was quantified by Flynn Wall Ozawa(FWO) and Vyazovkin and Weight(VW) model. It turned out that IMBPF/epoxy resin composites have three weight loss stages at the temperature ranges:300400, 400450 and 600700℃ , due to thermal decomposition of BPF, epoxy resin and nano CaCO3, respectively. The average activation energy of IMBPF/epoxy resin composites determined by two methods was higher than that of the control sample, and the value estimated by FWO method was higher than that by VW method. Nano CaCO3 has a regulatory effect on thermal degradation characteristics of composite. Meanwhile, there is only little difference between two methods which could provide theoretical support for the efficient utilization of plant fiber reinforced polymer composites.